February in the San Francisco Bay Area was warm. Our plum tree is in full blossom in mid-March, and the apricot tree blossoms have faded. We received 2/3 the normal rainfall in February, and February was very warm.
Los Altos Weather
We received 2.4 inches of rain in February, below the normal 3.3 inches.
Our rain this winter came in two bursts when the atmospheric river flowed through California. The West Without Water discussed mammoth floods and droughts in California’s past, and this shows how easily rain can come and go as the storm door opens and closes. From a Stanford study, “led by earth system science Professor Noah Diffenbaugh, offers new evidence of a tie. Diffenbaugh finds that warmer temperatures, driven by greenhouse gas emissions, have increased the prevalence of dry years on California’s historical record and will likely continue doing so in the decades to come.
More important, our normal rainfall drops after March as California enters the dry summer of our Mediterranean climate. Starting in April, our normal rainfall stays below an inch per month until November. The window for rain to break our drought is closing.
Just as important, the accumulated rainfall falls farther behind the normal.
Our February temperatures were much warmer than normal. For the first time in two years, the monthly high temperature was five degrees (F) above normal — it’s been close to normal the past two years. Our overnight low temperature was warmer than normal, continuing the trend of the past two years.
Drought persists or intensifies
The temperatures and rainfall are reflected in the Palmer Drought Severity Index. As shown below, much of California is in severe or extreme drought.
The forecast is for the drought to continue. The US weather service expects California’s drought to persist or intensify, with “below median precipitation” and “enhanced chances for above normal temperatures”. February’s pattern is expected to continue through March, when our rainfall normally drops.
From the March Water Tracker report, “March 2 Northern Sierra snowpack water content is about 21% of average for that date”. This is a record low for February: “In yet another disturbing sign of the multi-year drought, snowpack in California’s Sierra Nevada has plunged to a record nadir for late February. As of February 23, the snow depth at Donner Summit had fallen to its lowest total on record so late in the season, according to the University of California-Berkeley’s Central Sierra Snow Laboratory.”